Picture image monitoring system

ABSTRACT

A picture image monitoring system wherein picture images of a plurality of monitoring object areas and difference degree information indicative of a rate of a picture image change of each monitoring object area can be transmitted efficiently to a remote location by way of a communication channel and a monitoring operation of the monitoring object areas can be performed accurately and efficiently at the remote location. A transmitting side terminal apparatus and a receiving side terminal apparatus are interconnected by a communication channel. At the transmitting side terminal apparatus, a picture image signal of a monitoring object area photographed is compressed while difference degree information and an identifier are produced, and they are transmitted to the receiving side terminal apparatus by way of a communication line. At the receiving side terminal apparatus, received compressed picture image data, difference degree information and an identifier are used to effect detection of a picture image change of a monitoring object area and desired monitoring control.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a picture image monitoring system formonitoring a change of a picture image of a monitoring object area, andmore particularly to a picture image monitoring system which can effecta monitoring operation from a remote location by way of a communicationchannel.

2. Description of the Prior Art

An exemplary one of conventional picture image monitoring systems of thetype mentioned above is a monitoring camera system for the prevention ofcrimes. One of such conventional monitoring camera systems is shown inFIG. 14. Referring to FIG. 14, the monitoring camera system shownincludes a video camera positioned to photograph a monitoring objectarea, and a TV (television) monitor and a video tape recorder (VTR) bothconnected to the video camera. A picture image of the monitoring objectarea is photographed by the video camera and recorded by the VTR whileit is displayed on the TV monitor. A watching operation of the TVmonitor and a judging operation for occurrence of an abnormal conditionare performed by a watchman.

In this manner, with a conventional monitoring camera system for theprevention of crimes or a like monitoring system, a watching operationof a screen and a judging operation for occurrence of an abnormalcondition all rely upon manual operation. Consequently, there is aproblem that the accuracy in monitoring depends to a great extent uponfatigue or increase in stress of a watchman or upon a difference incapacity between individual watchman. Further, where manual operation isrelied upon, the detecting accuracy is high for such a great change of apicture image that occurs over an entire screen, but it is a problemthat a change of a picture image which occurs at a limited portion of ascreen is likely overlooked. It is another problem that, as the numberof monitoring object areas increases, the monitoring accuracy isdeteriorated to a great extent.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a picture imagemonitoring system which can transmit picture images of a plurality ofmonitoring object areas and difference degree information indicative ofrates of change of picture images of the monitoring object areas at ahigh efficiency to a remote location by way of a communication channelso that a monitoring operation at the remote location can be performedaccurately at a high efficiency.

In order to attain the object, according to the present invention, thereis provided a picture image monitoring system, which comprises atransmitting side terminal apparatus and a receiving side terminalapparatus connected to each other by way of a communication channel, thetransmitting side terminal apparatus including a plurality of imagepickup means for photographing individual monitoring object areas, apicture image signal selecting section for selecting one of pictureimage signals of the monitoring object areas photographed by the imagepickup means, a picture image data compressing section for compressing apicture image signal of a monitoring object area selected by the pictureimage signal selecting section, a picture image change detecting sectionfor detecting, from a picture image signal of a monitoring object areaselected by the picture image signal selecting section, a change of thepicture image of the monitoring object area to produce difference degreeinformation indicative of a degree of a difference of the picture imageof the monitoring object area and an identifier which specifies themonitoring object area then, and a communication circuit fortransmitting difference degree information and an identifier outputtedfrom the picture image change detecting section and compressed pictureimage data of a monitoring object area outputted from the picture imagedata compressing section to the receiving side terminal apparatus by wayof the communication channel and for receiving controlling informationfor the picture image monitoring transmitted thereto from the receivingside terminal apparatus by way of the communication channel, thereceiving side terminal apparatus including a communication circuit forreceiving difference degree information and an identifier as well ascompressed picture image data of a monitoring object area transmittedthereto from the transmitting side terminal apparatus by way of thecommunication channel and for transmitting controlling information forthe picture image monitoring to the transmitting side terminal apparatusby way of the communication channel, a compressed data decoding sectionfor decoding compressed picture image data received from thecommunication circuit into an original picture image, a controllinginformation generating section for producing predetermined controllinginformation for the picture image monitoring in accordance withdifference degree information and an identifier received from thecommunication circuit, and a picture image displaying section fordisplaying a picture image of a monitoring object area decoded by thecompressed data decoding section in accordance with controllinginformation outputted from the controlling information generatingsection.

In the picture image monitoring system, the image pickup means of thetransmitting side terminal apparatus may be installed such that they areindividually directed toward the respective predetermined monitoringobject areas to photograph them, and picture image signals photographedby the image pickup means are successively selected at a predeterminedinterval of time by the picture image signal selecting section.

The picture image data compressing section compresses the picture imagesignal of a monitoring object area selected by the picture image signalselecting section in accordance with a predetermined data compressingtechnique. Meanwhile, the picture image change detecting section maycompare the picture image of the current monitoring object area receivedfrom the picture image signal selecting section with a preceding pictureimage of the same monitoring object area to detect a change of thepicture image, and produces difference degree information indicative ofa degree of such change of the picture image as well as an identifierwhich specifies the monitoring object area then.

Such difference degree information and identifier from the picture imagechange detecting section and compressed picture image data from thepicture image data compressing section are transmitted to thecommunication circuit of the transmitting side terminal apparatus, fromwhich they are transmitted to the receiving side terminal apparatus byway of the communication channel.

The communication circuit of the receiving side terminal apparatusreceives such difference degree information and identifier as well ascompressed picture image data transmitted thereto from the transmittingside terminal apparatus. The compressed data decoding section decodesthe compressed picture image data back into an original picture imagesignal and sends the original picture image signal to the picture imagedisplaying section. Meanwhile, the controlling information generatingsection produces predetermined controlling information in accordancewith such difference degree information and identifier received from thecommunication circuit of the receiving side terminal apparatus and sendsit to the picture image displaying section. Further, when necessary, thecontrolling signal generating section sends such controlling informationalso to the transmitting side terminal apparatus by way of thecommunication channel so that predetermined picture image monitoringcontrol may be executed.

For example, the controlling information generating section maytransmit, to the picture image displaying section, controllinginformation to effect switching on or off of a monitor switch such that,when a change of a picture image is detected, the monitor switch isautomatically switched on to display a picture image of the monitoringobject area on a screen of the picture image displaying section. On theother hand, the controlling information generating section may transmit,to the transmitting side terminal apparatus, controlling information tocommand transmission only of a picture image of the monitoring objectarea in which the change of the picture image has occurred.

Thus, with the picture image monitoring system, a superior effect can beachieved that picture images of a plurality of monitoring object areasand difference degree information indicative of a rate of picture imagechange of each of the monitoring object areas can be transmittedefficiently to a remote location by way of the communication channel anda monitoring operation can be performed accurately with a high degree ofaccuracy at the remote location.

The above and other objects, features and advantages of the presentinvention will become apparent from the following description and theappended claims, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a fundamental construction of apicture image monitoring system according to the present invention;

FIG. 2 is a block diagram showing a transmitting side terminal apparatusof a picture image monitoring system according to the present invention;

FIG. 3 is a block diagram showing a receiving side terminal apparatus ofthe picture image monitoring system;

FIG. 4 is a diagrammatic view showing a Y component quantizing table;

FIG. 5 is a similar view but showing a C component quantizing table;

FIG. 6 is a diagram showing a manner of zigzag scanning;

FIGS. 7a and 7b are diagrammatic views showing a Huffman coding table;

FIGS. 8a to 8d are views illustrating data compressing processing for apicture image signal;

FIG. 9 is a diagrammatic view illustrating difference calculatingprocessing;

FIG. 10 is a similar view but illustrating another differencecalculating processing;

FIGS. 11a and 11b are diagrammatic views illustrating noise removingprocessing;

FIGS. 12a to 12d are similar views but illustrating another noiseremoving processing;

FIG. 13 is a diagrammatic view illustrating algorithm of differencedegree calculating processing executed by a picture image changedetecting section; and

FIG. 14 is a diagrammatic representation showing an exemplaryconstruction of a conventional monitoring camera system.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring first to FIG. 1, there is shown a fundamental construction ofa picture image monitoring system according to the present invention.The picture image monitoring system shown includes a set of atransmitting side terminal apparatus 1 and a receiving side terminalapparatus 2 connected to each other by way of a communication channel 8.

The transmitting side terminal apparatus 1 includes a plurality of imagepickup means 3₁ to 3_(n) for photographing respective monitoring objectareas, a picture image signal selecting section 4 for selecting one ofpicture image signals of the monitoring object areas photographed by theimage pickup means 3₁ to 3_(n), a picture image data compressing section5 for compressing a picture image signal of a monitoring object areaselected by the picture image signal selecting section 4, a pictureimage change detecting section 6 for monitoring, from a picture imagesignal of a monitoring object area selected by the picture image signalselecting section 4, a change of the picture image of the monitoringobject area to produce and output therefrom difference degreeinformation indicative of a degree of the change of the picture image ofthe monitoring object area and an identifier which identifies themonitoring object area then, and a communication circuit 7 fortransmitting difference degree information and an identifier outputtedfrom the picture image change detecting section 6 and compressed pictureimage data of a monitoring object area outputted from the picture imagedata compressing section 5 to the receiving side terminal apparatus 2 byway of the communication channel 8 and for receiving controllinginformation for the monitoring of picture image transmitted thereto fromthe receiving side terminal apparatus 2 by way of the communicationchannel 8.

Meanwhile, the receiving side terminal apparatus 2 includes acommunication circuit 9 for receiving difference degree information andan identifier as well as compressed picture image data of a monitoringobject area transmitted thereto from the transmitting side terminalapparatus 1 by way of the communication channel 8 and for transmittingtherefrom controlling information for the monitoring of a picture imageto the transmitting side terminal apparatus 1 by way of thecommunication channel 8, a compressed data decoding section 10 fordecoding compressed picture image data received by the communicationcircuit 9 back into an original picture image, a controlling informationgenerating section 12 for producing predetermined controllinginformation for the picture image monitoring in accordance withdifference degree information and an identifier received by thecommunication circuit 9, and a picture image displaying section 11 fordisplaying a picture image of a monitoring object area obtained bydecoding by the compressed data decoding section 10 in accordance withcontrolling information produced from the controlling informationgenerating section 12.

The image pickup means 3₁ to 3_(n) are installed such that they areindividually directed toward respective predetermined monitoring objectareas, and picture image signals photographed by the image pickup means3₁ to 3_(n) are successively selected at a predetermined interval oftime by the picture image signal selecting section 4.

The picture image data compressing section 5 compresses a picture imagesignal of a monitoring object area selected by the picture image signalselecting section 4 in accordance with a predetermined data compressingtechnique. Meanwhile, the picture image change detecting section 6compares the picture image of the current monitoring object areareceived from the picture image signal selecting section 4 with apreceding picture image of the same monitoring object area to monitor achange of the picture image, and produces difference degree informationindicative of a degree of such change of the picture image and besidesoutputs an identifier which identifies the monitoring object area then.

Such difference degree information and identifier from the picture imagechange detecting section 6 and compressed picture image data from thepicture image data compressing section 5 are transmitted to thecommunication circuit 7, from which they are transmitted to thereceiving side terminal apparatus 2 by way of the communication channel8.

The communication circuit 9 of the receiving side terminal apparatus 2receives such difference degree information and identifier as well ascompressed picture image data transmitted thereto from the transmittingside terminal apparatus 1. The compressed data decoding section 10decodes the compressed picture image data back into an original pictureimage signal and sends the original picture image signal to the pictureimage displaying section 11. Meanwhile, the controlling informationgenerating section 12 produces predetermined controlling information inaccordance with such difference degree information and identifierreceived from the communication circuit 9 and sends it to the pictureimage displaying section 11. Further, when necessary, the controllinginformation generating section 12 sends such controlling informationalso to the transmitting side terminal apparatus 1 by way of thecommunication channel 8 so that predetermined picture image monitoringcontrol may be executed.

For example, the controlling information generating section 12 maytransmit to the picture image displaying section 11 controllinginformation to effect switching on or off of a monitor switch not shownsuch that, when a change of a picture image is detected, the monitorswitch is automatically switched on to display a picture image of themonitoring object area on a screen of the picture image displayingsection. On the other hand, the controlling information generatingsection 12 may transmit to the transmitting side terminal apparatus 1controlling information to command transmission only of a picture imageof the monitoring object area in which the change of the picture imagehas occurred.

A picture image monitoring apparatus according to a preferred embodimentof the present invention is shown in FIGS. 2 and 3 wherein FIG. 2 showsa transmitting side terminal apparatus of the picture image monitoringsystem and FIG. 3 shows a receiving side terminal apparatus of thepicture image monitoring system.

Referring first to FIG. 2, the transmitting side terminal apparatusshown has a similar fundamental construction to that of the transmittingside terminal apparatus 1 shown in FIG. 1 and includes up to three videocameras 3₁ to 3₃ each serving as an image pickup means and disposedfixedly such that they are directed toward respective predeterminedmonitoring object areas so as to photograph the respective monitoringobject areas. The transmitting side terminal apparatus further includesa picture image signal selecting section 4, a picture image datacompressing section 5, a picture image change detecting section 6, and acommunication circuit 7.

The picture image signal selecting section 4 includes a video signalselecting circuit 401 for selectively outputting video signals receivedfrom the video cameras 3₁ to 3₃ cyclically at a fixed period, aY-separating circuit 402 for separating a video signal in the form of acolor composite signal received from the video signal selecting circuit401 into a Y (brightness) signal and a C (color difference) signal, anda pair of A/D (analog to digital) converters 403 and 404 forindividually converting Y and C signals received from the Y-C separatingcircuit 402 from analog signals into digital signals.

The picture image data compressing section 5 includes a two-dimensionalDCT (discrete cosine converting) circuit 501 for converting a Y signaland a C signal individually into orthogonal codes, a quantizing circuit502, a Y component quantization table 503, a C component quantizationtable 504, a coefficient order changing circuit 505 for scanningquantized two-dimensional DCT conversion coefficients in a zigzagfashion to re-arrange them such that they from a low frequency componenttoward a high frequency component, a differential PCM (pulse codemodulation) circuit 506 for converting a dc component of atwo-dimensional DCT conversion coefficient into a DPCM (differentialpulse code modulation) code, a zero packing circuit 507 for compressingterms of those of conversion coefficients which are equal to zero intocorresponding codes, a Huffman coding circuit 508 for converting thoseconversion coefficients other than 0 into corresponding Huffman codes, aHuffman coding table 509, and a signal combining circuit 510 forcombining a dc component and an ac component after such conversion intoa block.

The picture image change detecting section 6 includes a filter circuit601 for applying predetermined filtering processing to a Y signalreceived from the A/D converter 403 to extract a desired picture imagecharacteristic portion of the Y signal, an average value calculatingcircuit 602 for calculating a picture element density average value ofsuch extracted characteristic picture image, a binary digitizing circuit603 for converting such extracted characteristic picture image into abinary picture image consisting of the binary values of "1" and "0"using a picture element density average value calculated by the averagevalue calculating circuit 602 as a threshold value, a noise componentsuppressing circuit 604 for removing noise components from the binarypicture image, a variation calculating circuit 605 for calculating avariation of the picture element density average value of the pictureimage at present from another picture element density average value ofthe picture image in the past, a difference degree calculating circuit606 for producing difference degree information indicative of a degreeof a change of a picture image of a monitoring object area and anidentifier which identifies the monitoring object area then, a thresholdvalue setting circuit 607 for setting a threshold value for thedetection of a change of a picture image, and a picture image storagecircuit 608 for storing therein a binary picture image of a frame.

The communication circuit 7 receives compressed picture image data fromthe signal combining circuit 510 of the picture image data compressingsection 5 and a difference degree and an identifier from the differencedegree calculating circuit 606 of the picture image change detectingsection 6 and transmits the received information to the receiving sideterminal apparatus 2 shown in FIG. 3 by way of the communication channel8. The communication circuit 7 also receives controlling informationfrom the receiving side terminal apparatus 2 by way of the communicationchannel 8 and sends the received controlling information to thedifference degree calculating circuit 606 and also to the video signalselecting circuit 401 of the picture image signal selecting section 4.The communication channel 8 here may be any of the wire type and thewireless type.

In operation, video signals of the individual monitoring object areasphotographed by the video cameras 3₁ to 3₃ are successively andcyclically selected by the video signal selecting circuit 401 andinputted to the Y-C separating circuit 402.

A video signal inputted to the Y-C separating circuit 402 is separatedby the same into a Y (brightness) component and a C (color difference)component. The Y and C components thus obtained are then converted intodigital signals by the A/D converters 403 and 404, respectively, andthen transmitted to the two-dimensional DCT circuit 501, at which eachof them is divided into blocks of an 8×8 picture element size andtwo-dimensional DCT is effected for each of such blocks.

In particular, the two-dimensional DCT circuit 501 stores a Y componentand a C component of a video signal transmitted thereto from the Y-Cseparating circuit 402 once individually into frame memories not shownthereof, and for each of the signal components, a screen is divided intoblocks of an 8×8 picture element size. Then, for each block of each ofthe Y and C components, two-dimensional DCT is performed, when a pictureimage signal of the block is given by f(i, j) (u, v=0, 1, . . . , 7), inaccordance with the following expression to calculate a total of 8×8=64conversion coefficients F(u, v) for one block. ##EQU1##

The total of 8×8=64 conversion coefficients F(u, v) for each block thusobtained are sent to the quantizing circuit 502, at which they areindividually divided by quantization coefficients at correspondingpositions of the Y component quantization table 503 of FIG. 4 or the Ccomponent quantization table 504 of FIG. 5 and the quotients are roundedat decimals thereof to quantize the conversion coefficients F(u, v).Consequently, redundancy of the signals is removed.

The quantized conversion coefficients are scanned in a zigzag fashion asseen from FIG. 6 by the coefficient order changing circuit 505 so thatthe conversion coefficients are re-arranged from a lower one infrequency, using a dc component as a starting point, toward a higher oneand are read out in the re-arranged order. It is to be noted that, inFIG. 6, a hatched portion at the left upper corner represents a dccomponent.

The dc component read out by such zigzag scanning is sent to thedifferential PCM circuit 506, at which a difference thereof from a dccomponent of a preceding block is calculated and a difference value thusobtained is converted into a DPCM code. Meanwhile, ac components readout subsequently to the dc component are sent to the zero packingcircuit 507, at which those of them which have the coefficient 0 arezero packed in such a manner as hereinafter described, whereafter theyare Huffman coded by the Huffman coding circuit 508.

An exemplary procedure of data compression processing by the pictureimage data compressing section 5 is illustrated in FIGS. 8a to 8dwherein a block has a 4×4 picture element size in order to facilitatedescription.

Referring to FIGS. 8a to 8d, the block shown in FIG. 8a includes a totalof 4×4=16 conversion coefficients after quantization processingoutputted from the quantizing circuit 502. The 16 conversioncoefficients are zigzag scanned as illustrated in FIG. 8b by thecoefficient order changing circuit 505 and outputted as a coefficienttrain in which they are arranged in such an order as seen from FIG. 8c.

A coefficient value "4" (at position 1) of the first dc component in thecoefficient train of FIG. 8c read out by such zigzag scanning issubtracted from a dc component of a preceding block by the differentialPCM circuit 506 to obtain a difference between them, and a differencevalue thus obtained is coded and outputted as a DPCM value. It is to benoted that, when the block being processed is the first block, since nopreceding block exists, the coefficient value itself is coded andoutputted as a DPCM value. FIGS. 8a to 8d shows the case of such firstblock, and the coefficient value "4" is coded as it is and outputted asa DPCM value (4) as indicated at the position 1 of FIG. 8d.

On the other hand, as regards an ac component read out subsequently tothe dc component, first a number of consecutive terms of the coefficient"0" is coded with a code "RUN" by the zero packing circuit 507, and thenthe other terms of the other coefficients than zero are converted intoHuffman codes by the Huffman coding circuit 508 so that they are eachreplaced by a code bit length "SIZE" and a Huffman code "Index" afterconversion.

For example, as regards, for example, the first coefficient value "5"(at position 2) of the ac components in FIG. 8c, the value thereof isnot equal to 0, and consequently, the RUN code is "RUNO" whichrepresents that the coefficient is not equal to 0. Subsequently, if theHuffman coding table of FIG. 7 is referred to using the coefficientvalue "5" as an Index Value, it can be seen that, from the Code columnof the Huffman coding table, the coefficient value "5" is converted intoa Huffman code "101" while the code bit length is 3 bits from the CodeLength column. As a result, the coefficient value "5" is coded into"RUNO SIZE3 Index 5 (="101")" as seen from the position 2 of FIG. 8d.Also as regards the coefficient value "3" at the position 3, it issimilarly coded into "RUNO SIZE2 Index 3 (="11")".

Further, when the coefficient value "-1" is read out after thecoefficient value "0" continues by two as at the position 4 of FIG. 8c,since the consecutive number of terms of the coefficient value "0" is 2,the RUN code representative of a consecutive number of terms of "0" is"RUN2". Then, if the Huffman coding table of FIG. 7 is referred to usingthe coefficient value "-1" as an Index Value, then it can be seen that,from the Code column, the coefficient value "-1" is converted into aHuffman code "0" while the bit length is 1 from the Code Length column.As a result, the coefficient train (0, 0, -1) at the position 4 of FIG.8c is coded into "RUN2 SIZE1 Index -1 (="0")" as seen from the position4 of FIG. 8d.

Further, when the coefficient value "0" continues to the last end of ablock as at the position 8 of FIG. 8c, a special code EOB (End Of Block)representing that the coefficient value "0" continues to the last end ofthe block is added as seen from the position 8 of FIG. 8d.

The dc component and ac component coded in such a manner as describedabove are divided into blocks of such a predetermined format as seenfrom FIG. 8d by the signal combining circuit 510 and then sent to thecommunication circuit 7. The communication circuit 7 transmitscompressed picture image data sent thereto from the signal combiningcircuit 510 as well as difference degree information sent thereto fromthe difference degree calculating circuit 606 which will be hereinafterdescribed and representative of a degree of a change of a picture imageand an identifier (for example, a video camera number) also sent theretofrom the difference degree calculating circuit 606 and representative ofa monitoring object area then to the receiving side terminal apparatus 2by way of the communication channel 8.

Meanwhile, in parallel to such compressing processing of picture imagedata by the picture image data compressing section 5, such calculatingprocessing of difference degree information representative of a degreeof a change of the picture image of the monitoring object area asdescribed below is executed by the picture image change detectingsection 6.

In particular, the filter circuit 601 stores a Y signal transmittedthereto from the Y-C separating circuit 402 by way of the A/D converter403 once into a frame memory not shown thereof. Then, such differencecalculating processing as illustrated in FIG. 9 or 10 is applied to thepicture element data for one frame thus stored to produce a differencepicture image (edge picture image) of the picture image of themonitoring object area.

According to the difference calculating processing illustrated in FIG.9, when a picture element at the i-th position in the vertical directionand at the j-th position in the horizontal direction is determined as aprocessing object picture element y(i, j), a difference value Δy(i, j)of the processing object picture element y(i, j) is calculated inaccordance with the following expression:

    Δy(i, j)=y(i, j+1)+y(i+1, j)-2y(i, j)

Meanwhile, according the difference calculating processing illustratedin FIG. 10, which is called Laplachian processing, a difference valueΔy(i, j) of the processing object picture element y(i, j) is calculatedin accordance with the following expression:

    Δy(i, j)=y(i-1, j)+y(i, j-1)+y(i, j+1)+y(i+1, j)-4y(i, j)

It is to be noted that, in case a value of the difference value Δy(i, j)obtained in accordance with either of the expressions is in thenegative, the value is replaced by 0.

A difference picture image of a monitoring object area obtained by thedifference calculation processing of FIG. 9 or 10 described above is anedge picture image which is formed only from an edge or profileextracted as a picture image characteristic from an original pictureimage. The difference picture image of the monitoring object areaobtained in this manner is sent to the binary digitizing circuit 603 andaverage value calculating circuit 602.

The average value calculating circuit 602 adds {ΣΔy(i, j)} differencevalues Δy(i, j) of individual picture elements of the difference pictureimage of the monitoring picture area for the entire screen andcalculates a picture element density average value Δym of the differencepicture image in accordance with the following expression:

    Δym={ΣΔy(i, j)}/(number of picture elements added)

The picture element density average value Δym obtained in this mannerrepresents a degree at which picture element components are to beextracted from the monitoring object area then. When the value of thepicture element density average value Δym is high, the number of pictureelement components to be extracted from the monitoring object area isgenerally high, but on the contrary when the value of the pictureelement density average value Δym is low, the number of picture elementcomponents to be extracted from the monitoring object area is generallylow.

The binary digitizing circuit 603 converts a difference picture imagetransmitted thereto from the filter circuit 601 into a binary pictureimage consisting of the binary values of "1" and "0" using a pictureelement density average value Δym received from the average valuecalculating circuit 602 as a threshold value for the binarydigitization, and sends the binary picture image to the noise componentsuppressing circuit 604.

Meanwhile, the variation calculating circuit 605 calculates, using apicture element density average value or values in the past stored in amemory not shown thereof and a picture element density average value atpresent transmitted thereto from the average value calculating circuit602, a variation m of the picture element density average value atpresent with respect to the picture element density average value orvalues in the past in accordance with the following expression:

    m={current picture element density average value}/{average of picture element density average value or values in the past}

The variation m assumes m=1 when the amount of characteristic componentsto be extracted from the monitoring object area presents no change, butis m>1 when the amount presents an increase and m<1 when the amountpresents a decrease.

The noise component suppressing circuit 604 removes noise components ofa binary picture image. The noise removing processing is realized, inprinciple, by judging, preparing a mask of a predetermined size, forexample, such a mask of a 3×3 picture element size as shown in FIG. 11or 12, whether or not a picture element at the central position of themask is a noise in accordance with a distributing condition of thebinary values of "1" and "0" of picture elements around the centralpicture element. Such judging processing is performed displacing themask one after another picture element from the left end to the rightend of the upper end of the screen of the binary picture image, andafter the right end is reached, the mask is displaced by one pictureelement distance downwardly in the vertical direction and then similarprocessing is repeated from the left end to the right end again untilthe lower end of the screen is reached.

Exemplary procedures of noise removing processing will be described withreference to FIGS. 11 and 12. It is to be noted that such noise removingprocessing is performed only when a central picture element of a mask isequal to "1".

1 When only the central picture element is equal to "1" but all of theeight picture elements around the same are equal to "0":

The central picture element is regarded as a noise and replaced by "0".This is because, when only the central picture element is "1", it isconsidered to be an isolated point such as a noise.

2 When three or more picture elements around the central picture elementare equal to "1":

Since it is considered that the central picture element is not anisolated point such as a noise, it is left to be "1" as it is.

3 When only one picture element around the central picture element isequal to "1":

When the picture element of "1" is any one of picture elements atpositions marked with ◯ in FIG. 11a or 11b, the central picture elementis left as it is, but in any other case, the central picture element isregarded as a noise and replaced by "0".

In the case of FIG. 11a, since the processing proceeds from the left topto the right bottom of the binary picture image, a picture element at aposition marked with ◯ is a determined picture element for which it hasbeen judged whether or not it is a noise. Accordingly, when the pictureelement at a position marked with ◯ is "1", probably the central pictureelement is a picture element of "1" connecting to such picture element.

On the other hand, in the case of FIG. 11b, a picture element at aposition marked with ◯ is a picture element for which it will thereafterbe judged whether or not it is a noise, and when a picture element at aposition marked with ◯ is "1", probably the central picture element isan end point picture element of an edge connecting to the pictureelement at the position of ◯.

4 When two picture elements around the central picture element are equalto "1":

When only any two of picture elements at positions marked with ◯ are "1"as shown in FIG. 12a, the central picture element is left as it is, butotherwise, the central picture element is regarded as a noise andreplaced by "0". The judgment principle of the case of FIG. 12a issimilar to that of the case of FIG. 11a.

Further, when two of picture elements at positions marked with ◯ are "1"as shown in any one of FIGS. 12b to 12d, the central picture element isleft as it is, but otherwise, it is regarded as a noise and replaced by"0". This is intended, since a wrinkle of clothes which can be regardedas a noise upon picture processing appears in most cases as an edge lineof an L-shape, to remove such edge line as a noise and extract only anedge line of an L-shape, which is present frequently on a profile of anarticle, as significant picture elements.

A binary picture image from which noises have been removed in such amanner as described above is sent to the difference degree calculatingcircuit 606, at which a difference degree representative of a degree ofchange of a picture image of a monitoring object area is calculated insuch a manner as described below.

The algorithm in calculation of a difference degree of change of apicture image by the difference degree calculating circuit 606 isillustrated in FIG. 13. It is to be noted that FIG. 13 illustrates, forthe simplification of description, a case wherein the screen of a binarypicture image has a 4×4 picture element size and the picture imagestorage circuit 608 is constructed such that it stores therein twopicture images including a binary picture image of the last frame of amonitoring object area and another binary picture image of the secondlast frame.

Referring to FIG. 13, first, a binary picture image of the last frameand another binary picture image of the second last frame are read outfrom the picture image storage circuit 608 and the two picture imagesare logically ORed, and then, a logical OR picture image thus obtainedis reversed (complemented on one) to obtain a reverse picture image.

Subsequently, the reverse picture image and a binary picture image atpresent transmitted thereto from the noise component suppressing circuit604 are logically ANDed to obtain a logical AND picture image. Thelogical AND picture image obtained in this manner is a binary pictureimage which consists only of those picture elements which were equal to"0" in picture element density in the binary picture image in the pastbut present a change in picture element density from "0" to "1" in thebinary picture image at present.

The difference degree calculating circuit 606 counts a number of pictureelements of "1" in the logical AND picture image. The thus countedpicture element number is represented by P and indicates a total numberof picture elements which present the change from "0" to "1" in thebinary picture image of the monitoring object area at present. Thedifference degree calculating circuit 606 also counts a number ofpicture elements of "1" in the binary picture image at present. The thuscounted picture element number is represented by Q and indicates a totalnumber of picture elements of "1" in the binary picture image of themonitoring object area at present.

The difference degree calculating circuit 606 calculates a differencedegree using the picture element number P by which picture elements havechanged from "0" to "1", the total number Q of picture elements of "1"in the binary picture image of the monitoring area at present, athreshold value S for the judgment of a change of a picture image presetto the threshold value setting circuit 12 and the variation m of apicture element density average value transmitted thereto from thevariation calculating circuit 605, in accordance with the followingexpression:

    difference degree=(P/m)/(S×Q)

It is to be noted that, in the expression above, the threshold value Sspecifies a ratio of picture elements which have changed from "0" to "1"and varies within the range of S=0 to 1.0 (0% to 100%). Meanwhile, asdescribed hereinabove, the variation m is m=1 when the amount ofcharacteristic components to be extracted from the monitoring objectarea does not present a change, but is m>1 when the amount presents anincrease and m<1 when the amount presents a decrease.

The calculation expression for a difference degree given above has suchsignificance as follows. First, as a basic principle, a value (S×Q)obtained by multiplication of the total number Q of picture elements of"1" in the binary picture image by the predetermined threshold value Sis determined as a judgment boundary value for a change of a pictureimage, and a ratio=P/(S×Q) of the number P of picture elements whichhave changed from "0" to "1" to the boundary value (S×Q) is adopted as adifference degree of change of the picture image.

Accordingly, when a picture image has no change, since P=0, P/(S×Q)=0,which indicates that, when the difference degree is 0, there is nochange with the picture image. On the other hand, when P=(S×Q), that is,when the number P of picture elements which have changed from "0" to "1"is equal to the boundary value (S×Q), the difference degree is 1, and itcan be regarded that there is a picture image change in the monitoringobject area. As the picture element number P increases, the differencedegree increases farther than 1. Accordingly, it can be identified fromthe value of the difference degree how much picture image change hasoccurred in the monitoring object area.

Further, in accordance with the present invention, upon such calculationof a difference degree as described above, the number P of pictureelements which have changed from "0" to "1" is divided by the variationm of a picture element density average value indicative of a changingrate of characteristic components to be extracted from the monitoringobject area to effect correction in accordance with the change of thecharacteristic components to be extracted from the monitoring objectarea. Such correction is performed from the following reason.

If the amount of characteristic components to be extracted from themonitoring object area, for example, increases from that in the past,the number of picture elements of "1" in the binary picture image of themonitoring object area at present increases in proportion to suchincrease. Accordingly, in logical ANDing processing as seen in FIG. 13,the binary picture image of the monitoring object area at presentwherein the number of "1" has increased as the amount of characteristiccomponents has increased and a reverse picture image of the pictureimage of the monitoring area in the past are logically ANDed.

Consequently, the logical AND picture image obtained includes a number Pof picture elements which has increased from an original number ofpicture elements by a number by which characteristic components of themonitoring area have increased. A correct result of judgment cannot beobtained unless the number thus increased is cancelled. Thus, accordingto the present invention, the picture element number P is divided by thevariation m of the picture element density average value of the binarypicture image at present to return the picture element number P to itsoriginal picture element number. This makes it possible to find out anaccurate difference degree of change of a picture image even if theamount of characteristic components of a monitoring object area changes.

Here, a difference degree in the case of the example of FIG. 13 will becalculated. The number P of picture elements of "1" of the logical ANDpicture image is 8, and the number Q of picture elements of "1" in thebinary picture image at present is 11. Now, in case the threshold valueS is set to S=0.6 (60%) and the variation m of a picture element densityaverage value is m=1, that is, the amount of characteristic componentsof the monitoring object area presents no change, (P/m)=8/1=8 and(S×Q)=(0.6×11)=6.6, and the difference degree between them is 8/6.6÷1.2.Since the difference degree is higher than 1, it can be recognized thatthere is a picture image change in the monitoring object area.

In the meantime, in case characteristic components of the monitoringobject area have increased by 50% or so comparing with those in the pastand the variation m of the picture element density average value ism=1.5, (P/m)=8/1.5÷5, and consequently, the difference degree is5.3/6.6÷0.8. Since the difference degree is lower than 1, it can berecognized that there is no picture image change in the monitoringobject area.

The difference degree calculating circuit 606 sends difference degreeinformation obtained in such a manner as described above and indicativeof a degree of a picture image change of a monitoring object area and anidentifier (for example, a video camera number) which specifies themonitoring object area then to the communication circuit 7.

The communication circuit 7 transmits, at a point of time when both of aseries of compressed picture image data transmitted thereto from thepicture image data compressing circuit 5 and difference degreeinformation and an identifier from the picture image change detectingsection 6 are all prepared, such received compressed picture image data,difference degree information and identifier to the receiving sideterminal apparatus 2 by way of the communication channel 8.

Further, the communication circuit 7 receives predetermined controllinginformation transmitted thereto from the receiving side terminalapparatus 2 and executes predetermined picture image monitoring controlin accordance with the received controlling information such that, forexample, a selecting signal of the video signal selecting circuit 401 isfixed to one of the video cameras 3₁ to 3₃ which is photographing amonitoring object area in which there has been a picture image change sothat either only a picture image of the monitoring object area in whichthe abnormal condition has occurred is transmitted or calculatingprocessing of a difference degree by the difference degree calculatingcircuit 606 is stopped after a picture image change has occurred whileonly a picture image of the monitoring object area is transmitted.

It is to be noted that, after the series of difference degreecalculating processing is completed, a picture element density averagevalue or values in the past stored in the variation calculating circuit605 and a binary picture image or images in the past stored in thepicture image storage circuit 608 are updated to be prepared for nextprocessing.

Referring now to FIG. 3, the receiving side terminal apparatus shown hasa similar fundamental construction to that of the receiving sideterminal apparatus 2 of the picture image monitoring apparatus shown inFIG. 1. Thus, the receiving side terminal apparatus includes acommunication circuit 9, a compressed data decoding section 10, a TVmonitor 11 constituting a picture image displaying section and acontrolling information generating section 12. The receiving sideterminal apparatus additionally includes a signal discriminating section13 and a picture image recording video tape recorder (VTR) 14.

The signal discriminating circuit 13 receives data from thecommunication circuit 9 which receives such data from the transmittingside terminal apparatus 1 by way of the communication channel 8. Thesignal discriminating circuit 13 separates the received data intocompressed picture image data and the other data than the compressedpicture image data and transmits the compressed picture image data tothe compressed data decoding section 10 while it transmits differencedegree information and an identifier to the controlling informationgenerating section 12.

The compressed data decoding section 10 includes a conversioncoefficient separating circuit 101 for separating a dc component and accomponents of received compressed picture image data from each other, areverse differential PCM circuit 102 for changing a dc component backinto an original value, a Huffman decoding circuit 103 for decoding anac component into an original value, a Huffman decoding table 104, azero unpacking circuit 105 for changing a sequence of terms of thecoefficient 0 to an original value or values, a coefficient orderchanging circuit 106, a dequantizing circuit 107, a Y-componentdequantization table 108, a C-component dequantization table 109, atwo-dimensional IDCT circuit 110 for performing two-dimensional reversecosine conversion, and a Y-C composing circuit 111 for composing decodedY and C components to reproduce an original video signal (colorcomposite signal).

In operation, compressed picture image data of a monitoring object areaas well as difference degree information and an identifier transmittedfrom the transmitting side terminal apparatus 1 by way of thetransmission line 8 are received by the communication circuit 9 and thensent to the signal discriminating circuit 13. The signal discriminatingcircuit 13 sends the compressed picture image data in the received datato the compressed data decoding section 10 and sends the differencedegree information and identifier to the controlling informationgenerating section 12.

The compressed data decoding section 10 receiving the compressed datathus executes decoding processing of the compressed picture image datain the following manner.

In particular, the conversion coefficient separating circuit 101separates a dc component and ac components of the compressed data (referto FIG. 8d) from each other and sends the dc component to the reversedifferential PCM circuit 102 while it sends the ac components to theHuffman decoding circuit 103.

The reverse differential PCM circuit 102 adds a DPCM value of the dccomponent transmitted thereto from the conversion coefficient separatingcircuit 101 to another DPCM value of a dc component of the last block tofind out a conversion coefficient of an original dc component.Meanwhile, the Huffman decoding circuit 103 decodes the ac componentsinto an original conversion coefficient referring to the Huffmandecoding table 104 while the zero unpacking circuit 105 decodes a termof the conversion coefficient 0 into an original coefficient train.

The conversion coefficients of the dc component and ac componentsdecoded into original values in such a manner as described above areindividually sent to the coefficient order changing circuit 106, atwhich the order of them is re-arranged by zigzag scanning so that theyare decoded back into an original block of 8×8=64 conversioncoefficients shown in FIG. 6.

The 64 conversion coefficients for each of the Y and C componentsreturned into original conversion coefficient blocks are sent to thedequantizing circuit 106, at which the 64 conversion coefficients forthe Y and C components are multiplied by values at correspondingpositions of the Y component dequantizing table 108 and C componentdequantizing table 107, respectively, so that they are individuallyreturned into original 8×8=64 conversion coefficients F (u, v) beforequantization.

The conversion coefficients F (u, v) undergo two-dimensional reversecosine conversion in accordance with the following expression for eachof the Y component and C component by the two-dimensional IDCT circuit110 so that they are returned into an original signal f(i, j). ##EQU2##

The Y and C signals individually returned into original signals f(i, j)on the time base in this manner are composed into an original videosignal (color composite signal) by the Y-C composing circuit 111 andthen sent to the TV monitor 111 serving as a picture image displayingsection and also to the VTR 14. After then, the processing described sofar is repeated until the received compressed picture image data no moreremain.

Meanwhile, the controlling information generating section 12 producespredetermined controlling information in accordance with differencedegree information and an identifier transmitted thereto from the signaldiscriminating circuit 13 to effect predetermined control of the TVmonitor 11 serving as a picture image displaying section and the VTR 13and sends controlling information to the transmitting side terminalapparatus 1 to effect predetermined control.

For example, the controlling information generating section 12 controlson/off operations of switches not shown of the TV monitor 11 and the VTR14 so that, when some picture image change occurs in a monitoring objectarea, the picture image of the monitoring object area is automaticallydisplayed on the TV monitor 11 and the picture image is recorded by theVTR 14.

Further, the controlling information generating section 12 controls thetransmitting side terminal apparatus 1 such that, for example, itcontrols the video signal selecting circuit 401 so that only a videosignal of a monitoring object area in which a picture image change hasoccurred is transmitted and, further, at a point of time when thepicture image change occurs, a difference degree calculating operationof the difference degree calculating circuit 606 is stopped, whereafterit instructs so that only picture image data may be transmitted to thereceiving side terminal apparatus 2 side.

It is to be noted that, while the embodiment described above isconstructed such that a color composite signal is employed as a pictureimage signal, naturally it can be realized similarly where amonochromatic signal is employed. In this instance, those circuits whichrelate to a C (color difference) component in FIGS. 2 and 3 can beomitted.

Further, while two-dimensional DCT is adopted for the compression ofpicture image data in the embodiment described above, the presentinvention is not limited to such two-dimensional DCT, but any otherpicture image compressing technique may be adopted.

Further, while the filter circuit 601 of FIG. 2 adopts differencecalculation to extract a high frequency component, optimum filteringprocessing may be adopted in accordance with a purpose of the monitoringof a picture image such as low frequency component extraction or bandcomponent extraction.

Further, while a variation m of a picture element density average valueat the variation amount calculating circuit 605 is calculated as a ratioto an average of picture element density average values of a pluralityof frames in the past, a substantially mid value or a most frequentvalue of such picture element density average values of a plurality offrames in the past may be used to find out such ratio in order tosimplify processing.

Further, while the difference value calculating circuit 606 makes use ofa variation m of a picture element density average value as it isdirectly for calculating processing of a difference degree, it is alsopossible to effect finer calculating processing by numerical valueconversion in accordance with a function making use of such variation mas a variable such as stepwise increasing or decreasing of the variationor fixation of the variation to a fixed value when the variation exceedsa certain value.

Further, controlling information of the controlling informationgenerating section 12 of FIG. 3 may be produced, after difference degreeinformation is displayed once on a display to inform a watchman of suchinformation, in accordance with an instruction of the watchman, oralternatively, the controlling information generating section 12 mayautomatically perform all operations without relying upon a watchman.Where all operations are performed automatically, whether or not therehas been a change of a picture image of a monitoring object area shouldbe detected depending upon whether or not the difference degree receivedfrom the transmitting side terminal apparatus 1 exceeds "1" as describedhereinabove. Further, it is also possible to inform a watchman ofoccurrence of an abnormal condition making use of such controllinginformation or by acoustic or optical alarming means.

Having now fully described the invention, it will be apparent to one ofordinary skill in the art that many changes and modifications can bemade thereto without departing from the spirit and scope of theinvention as set forth herein.

What is claimed is:
 1. A picture image monitoring system, comprising atransmitting side terminal apparatus and a receiving side terminalapparatus connected to each other by way of a communication channel;saidtransmitting side terminal apparatus including: a plurality of imagepickup means for respectively photographing individual monitoring objectareas and generating a plurality of respective picture image signals; apicture image signal selecting section for selecting one of saidplurality of picture image signals of the monitoring object areasphotographed by a respective one of said plurality of image pickupmeans; a picture image data compressing section for compressing the onepicture image signal selected by said picture image signal selectingsection; a picture image change detecting section for detecting, fromthe one picture image signal selected by said picture image signalselecting section, a change of the one picture image signal of themonitoring object area, and for producing difference degree informationindicative of a degree of a difference of the one picture image signaland producing an identifier which specifies the monitoring object areacorresponding to the one picture image signal; and a communicationcircuit for transmitting the difference degree information, theidentifier outputted from said picture image change detecting section,and the compressed picture image data of a monitoring object areaoutputted from said picture image data compressing section to saidreceiving side terminal apparatus by way of said communication channel,and for receiving controlling information for selection of the pictureimage data to be transmitted by way of said communication channel; saidreceiving side terminal apparatus including: a communication circuit forreceiving difference degree information and an identifier as well ascompressed picture image data of a monitoring object area transmittedthereto from said transmitting side terminal apparatus by way of saidcommunication channel and for transmitting controlling information forselection of the picture image to be transmitted by way of saidcommunication channel; a compressed data decoding section for decodingcompressed picture image data received from said communication circuitinto an original picture image; a controlling information generatingsection for producing predetermined controlling information forselection of the picture image data to be transmitted in accordance withdifference degree information and an identifier received from saidcommunication circuit; and a picture image displaying section fordisplaying the picture image signal of a monitoring object area decodedby said compressed data decoding section in accordance with controllinginformation outputted from said controlling information generatingsection.
 2. A picture image monitoring system as claimed in claim 1,wherein said receiving side terminal apparatus further includesrecording means for recording an original picture image from saidcompressed data decoding section onto a record medium in accordance withcontrolling information from said controlling information generatingsection.
 3. A picture image monitoring system, comprising a transmittingside terminal apparatus and a receiving side terminal apparatusconnected to each other by way of a communication channel;saidtransmitting side terminal apparatus including; a plurality of imagepickup means for respectively photographing individual monitoring objectareas and generating a plurality of respective picture image signals; apicture image signal selecting section for selecting one of saidplurality of picture image signals of the monitoring object areasphotographed by a respective one of said plurality of image pickupmeans; a picture image data compressing section for compressing the onepicture image signal selected by said picture image signal selectingsection; a picture image change detecting section for detecting, fromthe one picture image signal selected by said picture image signalselecting section, a change of the one picture image signal of themonitoring object area, and for producing difference degree informationindicative of a degree of a difference of the one picture image signaland producing an identifier which specifies the monitoring object areacorresponding to the one picture image signal; and a communicationcircuit for transmitting the difference degree information, theidentifier outputted from said picture image change detecting section,and the compressed picture image data of a monitoring object areaoutputted from said picture image data compressing section to saidreceiving side terminal apparatus by way of said communication channel,and for receiving controlling information for selection of the pictureimage data to be transmitted by way of said communication channel; saidreceiving side terminal apparatus including: a communication circuit forreceiving difference degree information and an identifier as well ascompressed picture image data of a monitoring object area transmittedthereto from said transmitting side terminal apparatus by way of saidcommunication channel and for transmitting controlling information forselection of the picture image to be transmitted by way of saidcommunication channel: a compressed data decoding section for decodingcompressed picture image data received from said communication circuitinto an original picture image; a controlling information generatingsection for producing predetermined controlling information forselection of the picture image data to be transmitted in accordance withdifference degree information and an identifier received from saidcommunication circuit; and a picture image displaying section fordisplaying the picture image signal of a monitoring object area decodedby said compressed data decoding section in accordance with controllinginformation outputted from said controlling information generatingsection. wherein said receiving side terminal apparatus further includesa signal discriminating circuit for receiving data from saidcommunication circuit of said receiving side terminal apparatus andseparating the received data into compressed picture image data to betransmitted to said compressed data decoding section and differencedegree information and an identifier to be transmitted to saidcontrolling information generating section.
 4. A picture imagemonitoring system, comprising a transmitting side terminal apparatus anda receiving side terminal apparatus connected to each other by way of acommunication channel:said transmitting side terminal apparatusincluding: a plurality of image pickup means for respectivelyphotographing individual monitoring object areas and generating aplurality of respective picture image signals; a picture image signalselecting section for selecting one of said plurality of picture imagesignals of the monitoring object areas photographed by a respective oneof said plurality of image pickup means; a picture image datacompressing section for compressing the one picture image signalselected by said picture image signal selecting section; a picture imagechange detecting section for detecting, from the one picture imagesignal selected by said picture image signal selecting section, a changeof the one picture image signal of the monitoring object area, and forproducing difference degree information indicative of a degree of adifference of the one picture image signal and producing an identifierwhich specifies the monitoring object area corresponding to the onepicture image signal; and a communication circuit for transmitting thedifference degree information, the identifier outputted from saidpicture image change detecting section, and the compressed picture imagedata of a monitoring object area outputted from said picture image datacompressing section to said receiving side terminal apparatus by way ofsaid communication channel, and for receiving controlling informationfor selection of the picture image data to be transmitted by way of saidcommunication channel; said receiving side terminal apparatus including;a communication circuit for receiving difference degree information andan identifier as well as compressed picture image data of a monitoringobject area transmitted thereto from said transmitting side terminalapparatus by way of said communication channel and for transmittingcontrolling information for selection of the picture image to betransmitted by way of said communication channel; a compressed datadecoding section for decoding compressed picture image data receivedfrom said communication circuit into an original picture image; acontrolling information generating section for producing predeterminedcontrolling information for selection of the picture image data to betransmitted in accordance with difference degree information and anidentifier received from said communication circuit; and a picture imagedisplaying section for displaying the picture image signal of amonitoring object area decoded by said compressed data decoding sectionin accordance with controlling information outputted from saidcontrolling information generating section. wherein said picture imagechange detecting section of said transmitting side terminal apparatusincludes a filter circuit for applying predetermined filteringprocessing to the one picture image signal selected by said pictureimage signal selecting section to extract a predetermined picture imagecharacteristic of the picture image signal, an average value calculatingcircuit for calculating a picture element density average value of anextracted characteristic picture image from said filter circuit, abinary digitizing circuit for converting an extracted characteristicpicture image from said filter circuit into a binary picture image usinga picture element density average value calculated by said average valuecalculating circuit as a threshold value, a variation calculatingcircuit for calculating a variation of a picture element density averagevalue of a picture image at present from another picture element densityaverage value of the picture image in the past, and a difference degreecalculating circuit for producing difference degree information and anidentifier in accordance with a binary picture image from said binarydigitizing circuit, a variation from said variation calculating circuitand a picture image from said picture image signal selecting section. 5.A picture image monitoring system as claimed in claim 4, wherein saidpicture image change detecting section of said transmitting sideterminal apparatus further includes a picture image storage circuit forstoring therein at least one binary picture image of a frame from saidbinary digitizing circuit.
 6. A picture image monitoring system asclaimed in claim 4, wherein said picture image change detecting sectionof said transmitting side terminal apparatus further includes a noisecomponent suppressing circuit interposed between said binary digitizingcircuit and difference degree calculating circuit for removing noisecomponents from a binary picture image from said binary digitizingcircuit.
 7. A picture image monitoring system as claimed in claim 4,wherein said picture image change detecting section of said transmittingside terminal apparatus further includes a threshold value settingcircuit for setting a threshold value S, and wherein said differencedegree calculating circuit calculates a difference degree using apicture element number P by which picture elements of a binary pictureimage from said binary digitizing circuit have changed from "0" to "1"of the binary values, a total number Q of picture elements of "1" insuch binary picture image at present, a variation m of a picture elementdensity average value from said variation calculating circuit and thethreshold value S from said threshold value setting circuit, inaccordance with the following expression:

    difference degree=(P/m)/(S×Q)